Wind turbines are well known in the art for low cost power generation in areas of relatively consistent wind. Other than moderate noise pollution, these wind turbines are pollution free and have relatively low operating costs. However, the present wind turbines can have a high initial investment cost, and their performance can vary depending on wind direction and guidance machinery to maintain the turbine in position for maximum power output.
Wind turbines comprise two general types, horizontal axis and vertical axis. The vertical axis wind turbine is the simplest design, and one predominant vertical axis wind turbine is commonly referred to as a Savonius wind turbine. Savonius-type wind turbines are well known in the art. Examples are illustrated in U.S. Pat. No. 4,784,568, U.S. Pat. No. 4,359,311, and U.S. Pat. No. 5,494,407. The rotor blades or vanes are traditionally semi-cylindrical shaped and coupled to a central shaft. FIG. 1 illustrates a perspective view of a traditional Savonius vertical axis wind turbine and FIG. 2 illustrates a cross section of a vertical axis wind turbine with Benesh airfoils. The principle of operation of Savonius wind turbine machine is based on the difference in the drag forces of semi-circular vanes extending horizontally on a rotor, where one semi-circular vane is oriented so as to be concave while the counterpart vane is oriented to be convex. When placed in an air stream, the drag difference between the concave vane and the convex vane causes the rotor to rotate. Advantages of this type of machine are that it is self-starting, does not require aiming into an incident wind direction, is simple to design, and has low construction cost. However, previous extensive experimental studies have shown that it has relatively low efficiency.